Adjustable resistance unit



Sept. 8, 1925.

'E. A. EVERETT ADJUSTABLE RESISTANCE UNIT 2 Sheets-Sheet 1 Filed Oct. 16. 1924 INVENTOR. wwfl z m Sept. 8, 1925.

. E. A. EVERETT ADJUSTABLE RESISTANCE UNIT Filed Oct. 16, 1924 2 Sheets-Shoat 2 IN VEN TOR. Z 2 M wi Patented Sept. 8, 1925.

UNITED STATES PATENT {O F F I C E g ADJUSTABLE 'BESIS'IANGE UN-IT np plication flled octpber 16,1924. Serial No. '244,081.

v To all whom it may poncem:

Be itknoWn that I, EDWARD A. EVERETT,

I a citizen of the United States, and resident vented certain new and useful; Adjustable. Resistance Units, of which the following is;

Queens and State of New York, have in a specification.

ance units for use in electric circuits and has for ,an object to provide a resistance r ,unit of thistype Which is readilyadj ustable which makes a positiveconnection, in which;

the value of the resistance in the circuit can ireadily be computed andin which the'main.

connections are not disturbed when the value of the res] stance 1S changed.

With means for holding these links in a fixed position When theyware not used forshunt ing purposes, also,.discharge points between where it is readily inspected andis not subject to excessive temperature changes.

' These and other-objects of the invention Will be more particularly understood fromthe following specification andthe accompanying drawings in which Fig. l is a top View of acircular resistance unit embodying v.myinverition; Fig; 2 is the interior bottom .vieW of a resistance unitcorresponding to, Fig. 1; Fig. 3 is a sectional elevation of a; resistance unit similar o llig. 1 and L- Lis. a. diagram showingfthe electrical pcone. .nections. i V

. 5is an interior hottomwview of a resistance. unit of. larger capacity than. Rig. 1

. embodying my invention and Fig. G is a top view :of the. unit shown in. Fig; 5.,

,Fig. 7' is'a side elevation of a small sized used" inv I railway signal work. for track cir- J This invention relates to adjustable resist- A further object of the invention resides-in the use of links for shunting the resistance coils purposes. 5 .The objects are to obtain a comparatively inexpensive resistance unit which can be quickly adjusted and the value of the of Long Island City, in the county of resistance readily determined, to make posit ve connections and to insure that the parts willnot become niisplacedby vibration and thejconditions; of service. Slide type resistance coils adjustableby a sliding contact do not make the-positiveconnection desired and resistance coils made in multiple units With combination series-multiple connections are diiii cult [to determine the value of the resistance.

' the present invention a single coil of wlire of uniform size isused loopedaround adjaceritlter minals so-as to include a fixed resistancebetween these terminals; On the top of the casing a; link is used to bridge adjacent terminals and thus shunt the resistance. VVhen'this link is not used for shunt ng purposes it is placed radially on the device Where it -engages With the porcelain-casing and is rigidly'held in this position; it is impossible therefore, for these links to become I misplaced or; accidentally Imake contact with-each other.- When the links areplaced in the radial position the innerends are;comparatively close together;

these,- ends. are provided With discharge points so that they act as. a lightning arrester shuntto discharge high potential currents from the resistance coil.

Besista-ncecoils of ,this type are freguently requiredto; carry heavy currents for considerable intervals. This leads to the heating of the coil and' it is found in practice: that an alloy Wireof the kind used in; these coils makes an unreliable contact with theterminal post due to these intermit 1-.tent heatings; In the present invention therefore-the resistance coil; is enclosed in a porcela n liOIlSlDg- -bUL-thG*COl'lIlGClZlQIl to the binding-jpost is madeonthe outside of the porcelain Where it cannot .becomeexcessive iy I heated, and: Where it is :readily inspected.

-;;-Referring,to.the drawings, 11; is a hollow porcelain ,containenhaving the base 12 ,which is. ;secu-r-ed, thereto by. the; central ,.SQI-6 W"13,-, Wl1i0h passesthrough and-is in- I sulatedl=byithe'isleeve '15. The interior of resistance unit embodying theieatnresof my inventionand Fig} 8is atop. view not Rig. 7 Resistance units sofv the character con .templated by hisinvention are .extensively gmade-from the-same gage-wire have differi I l entvalues flSs determinedbythe length of theicontainer isatlivided-iby ribs 1411s indi- .cated in Fig. 2 to provide pockets 'for the resistance @coils. "j The; resistance coils when 1.8. These coils are placed both vertical and horizontal as indicated in Fig. 2 according to their size and the space available.

A row of terminal posts 21, 22, 23, 2 25, 26, 27 and 28 are centrally spaced on the top of the housing and around each of these terminal posts the resistance wire is looped as indicated in Fig. It will be noted that the coil is preferably, an endless wire looped around the terminal posts with a resistance unit between each pair of terminals. The coil starts at 21 and ends at 22, these are therefore the main terminals to which the conductors 4L1 and l2 are connected.

A link 29 having a slot is placed over each of the terminal posts and is provided with a jaw 31. These links will bridge any pair of adjacent terminal posts by moving on the slot until the jaw engages the adjoining post when it is clamped in position by the binding nut and lock nut as indi cated between the posts 21 and 27 inclusive Fig. 1. The resistance of the link and its connection to the post is assumed to be zero so that the resistance coils between these terminals are shunted. Yi hen a link is not used for bridging purposes it is placed in the position shown on posts 22 and 28. That is, the longitudinal. ot the link is ra dially disposed. on the circular top and the jawed end is placed in a recess 34lot the elevated central section 33 ot the porcelain top. In operation, the nuts are lacked oil? and. the links are raised until they fall into the recess and when the nuts are tightened the links are securely held by the sides oi? the recess and by the post engaging the inner end of the slot; adjoining links there- ;Fore cannot swing around and shunt the resistance coil. The oppos ng edges ot the inner end of the links are provided with saw teeth as at w iich constitute a spar-lo p arrester for the cischarge oi? lightning ich, otherwise would pass through the resistance coil with possible injury thereto.

The value of the resistance is indicated by figures onv the porcelain top between the iern'iinal posts as indicated by the figures 1/10. 2/10; 8/10; 4/10, 1, l, and 2 in Fig. be noted that these figures are d when the links are in the position but are tully exposed links are in the non-shunting position. The value of the resistance in circuit is the sum of the resistance between the posts which are not shunted.

Opposite each terminal post an oblong slot 36 is made in the cover for the passage of the loop such as 37, Fig. 3, of the resistance wire to the outside and around the terminal post where it is clamped in place by the binding nut at 38. This removes the connection from the interior of the housing which is subject to temperature variation in the resistance coil, to the outside of the casing exposed to the atmosphere, and also, to a position where the connection can always be inspected. This is an important feature when alloy wire is used as itwould not be possible to obtain a reliable connection by clamping this wire under the interior head of the terminal post and this wire cannot be soldered.

A ledge 43 is formed around the casing equal in diameter to the extension of the links 29 to act as a shield for these links. This ledge may be formed in a series 01 ridges registering with the links in the non: shunting position.

It will be noted that the elevation of ledge t is gr ater than the corresponding ledge on the opposite side as this ledge is formed on a spiral indicated by the dotted line. The object of this spiral elevation is to so arrange the links that the slot end ct one passes below the jaw end of the next progressively around the terminal posts.

in adjusting the resistance it should he noted that the wire connections to the main terminals are never disturbed, the adjustment being made by the links as desired.

The resistance unit shown in Fig. 5 is constructed along the lines described. This is tor a larger unit with more coils and is ohlong in shape. The casing "i6 is provided with an annula r pocket 4.7 housing a long re sistance coil and a central pocket "l8 houses a double resistance coil. The terminal posts are arranged in a row betweei'i these two sets oi resistance coils. The resistance coi s be tween tern'iinals may be arranged vertically or horizontally a desired and ucwrding; to the space available.

The top is provided with an elevate. ledge 51 having pockets or recesses formed therein opposite each teri'ninal post to receive the tree end ot the connecting link and hold it in the non-shunting iiosition. The main lern'iinals are indicated at it? and 50 and as shown in 6 the resistance ilk tween these terminals is Gf ohuis.

A small type ot resistance unit shown in Figs. 7 and 8. Five terminal posts indi cated by 62, 63, 64-, 65 and (16 are provided:

and being the inai trrniinalsi A of links 29 are placed on post iE'w-land a FIDU- lar pair are placed on post 66. These our links may be used to bridge all the terminal posts from 62 to 63 as indicated by the full and dotted lines, or one link may be used to shunt any pair and the other link placed in the non-shunting position, or both links may be placed in the non-shunting position.

The links on post 66 are held in the nonshunting position by the projection 67 from the porcelain top and the links on post 6% are similarly held by projection 68. These projections engage the slot of the link and will engage one or both links at the same time. W'hen the links are placed over these inn projections and clamped by the binding nuts they are securely held in the non-shunting.

nections to be made in a positive and reliable manner.

Having thus described my invention, I claim:

1. In an adjustable resistance unit of the class described, the combination of a housing, a plurality of resistance coils in said housing, a terminal post connected between each pair of resistance coils, links connecting said terminals for shunting said coils and means associated with said housing for holding said links in the non-shunting position.

2. In an adjustable resistance unit of the class described, the combination of a housing, a plurality of resistance coils in said housing, a terminal post connected between each pair of resistance coils, links connecting said terminal posts for shunting said coils and pockets in said housing co-operating with said posts for holding said links in the non-shunting position.

3. In an adjustable resistance unit of the class described, the combination of a housing, a plurality of resistance coils in said housing, a terminal post connected between each pair of resistance coils, links connecting said terminal posts for shunting said coils, a projection on said housing and means whereby said links may be brought into engagement with said projection and held rigidly thereby when in the non-shunting position.

4. In an adjust-able resistance unit of the class described, the combination of a housing, a plurality of resistance coils in said housing, a terminal post connected between each pair of resistance coils, a link on each post having discharge points at one end and means whereby said links may be used to shunt said resistance coils and may be positioned to act as a lightning arrester for said coils.

5. In an adjustable resistance unit of the class described, the combination of a housing, a plurality of resistance coils in said housing, a terminal post connectedbetween each pair of resistance coils, a link on each post having discharge points at one end, means whereby said links may be used to shunt said resistance coils and means associated with said housing for holding said links in a fixed position to act as a lightning arrester.

6. In an adjustable resistance unit of the class described, the combination of a l1ousing, a plurality of resistance coils in said housing, a terminal post connected between each pair of resistance coils, a link having a slotted opening at one end and a aw at the other end engaging each post, said link arranged to engage a pair of adjacent posts when the post is at one end of the slot and to be firmly engaged by a projection on said housing when the post is at the opposite end of the slot.

7. In an adjustable resistance unit of the class described, the combination of a housing, a plurality of coils in said housing, a terminal post connected between each pair of resistance coils, a link on each post for connecting to the adjacent post, said posts arranged on said housing each on a. higher elevation than the preceding post whereby the end of one link will overlap the end of the link on the adjacent post.

8. In an adjustable resistance unit of the class described, the combination of a housing, a plurality of coils in said housing connected in series, said coils having fixed resistance indicated by numerals on the cover of said housing, terminal post connected between each pair of coils and extending through said cover, slotted links for bridging said terminal posts, said links when in the bridging position partially covering said numerals.

Signed at New York in the county of New York and State of New York this 14th day of October A. D. 1924.

. EDIVARD A. EVERETT. 

